Remote systems, such as vehicles, have been introduced that include locomotion power derived from electricity received from an energy storage device, such as a battery. For example, hybrid electric vehicles include on-board chargers that use power from vehicle braking and traditional motors to charge the vehicles. Vehicles that are solely electric generally receive the electricity for charging the batteries from other sources. Battery electric vehicles (also referred to as simply “electric vehicles”) are often designed to be charged through some type of wired alternating current (AC) such as household or commercial AC supply sources. The wired charging connections involve cables or other suitable connectors that are physically connected to a power supply. Cables and other connectors may sometimes be inconvenient or cumbersome and may have other drawbacks. Wireless power charging systems that are capable of transferring power in free space (e.g., via a wireless field) to charge electric vehicles may overcome some of the deficiencies of wired charging solutions. As such, wireless power charging systems and methods that efficiently and safely transfer power for charging electric vehicles are desirable.
Inductive power transfer (IPT) systems are one means for the wireless transfer of energy. In IPT, a primary (or “base”) power device (e.g., a base pad, base wireless charging system, or some other wireless power transmitting device including a power transfer element (e.g., base power transfer element)) transmits power to a secondary (or “pick-up”) power receiver device (e.g., a vehicle pad, an electric vehicle wireless charging unit, or some other wireless power receiving device including a power transfer element (e.g., vehicle power transfer element)). Each of the transmitter and receiver power devices includes inductors, typically coils or windings of electric-current-conveying media. An alternating current in the primary inductor of the primary power device produces a fluctuating magnetic field. When the secondary inductor is placed in proximity to the primary inductor, the fluctuating magnetic field induces an electromotive force (EMF) in the secondary inductor, thereby transferring power to the secondary power receiver device.